Composite

This chapter is dedicated to composing objects within one another, so it may look strange to have a separate section for the Composite design pattern. As a result, this raises a question:

Shouldn't this design pattern encompass all of the others?

As in the case of the Bridge design pattern, the name may not reflect its true uses and benefits.

Let's continue with our StormTrooper example from before. Lieutenants of the Empire quickly discover that no matter how well equipped, stormtroopers cannot hold their ground against the rebels because they are uncoordinated.

To provide better coordination, the Empire decides to introduce the concept of a squad for the stormtroopers. A squad should contain one or more stormtrooper of any kind, and when given commands, it should behave exactly as if it was a single unit.

Squad, clearly, consists of a collection of stormtroopers:

class Squad(val units: List<Trooper>)

Let's add a couple of them to...